Wstęp

This extension filters data by either validating or sanitizing it. This is
especially useful when the data source contains unknown (or foreign) data,
like user supplied input. For example, this data may come from an HTML form.

There are two main types of filtering:
validation and sanitization.

Validation is used to
validate or check if the data meets certain qualifications. For example,
passing in FILTER_VALIDATE_EMAIL will determine if
the data is a valid email address, but will not change the data itself.

Sanitization will
sanitize the data, so it may alter it by removing undesired characters.
For example, passing in FILTER_SANITIZE_EMAIL will
remove characters that are inappropriate for an email address to contain.
That said, it does not validate the data.

Flags are optionally used with both validation and
sanitization to tweak behaviour according to need. For example, passing
in FILTER_FLAG_PATH_REQUIRED while filtering an
URL will require a path (like /foo
in http://example.org/foo) to be present.